function f () {
    var a  = 1;
    let b = 2;
    {
      let  b =  3;
      var c = 4;
      let d = 5;
      debugger;
      console.log(a, b, c, d) //  1 3 4 5
    }
    {
    //   let b =  6;
      let d = 7;
      console.log(a, b, c, d)  //  1 6 4 7
    }
  }
  f()
  